Finding the Fourth Proportional to 1,139.67, 1,572.76 and 642.32

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.67 : 1,572.76 = 642.32 : x
2. Step 2: Convert to fraction form
   1,139.67/1,572.76 = 642.32/x
3. Step 3: Cross multiply
   1,139.67x = 1,572.76 × 642.32
4. Step 4: Simplify right side
   1,139.67x = 1,010,217.53
5. Step 5: Solve for x
   x = 1,010,217.53/1,139.67
6. Step 6: Final answer
   x = 886.41